The difficulty of covering all interior surfaces of the tubes from the very top down to the bottom is compounded by the need to wash the tubes sequentially with a series of different cleaning fluids as a part of the recommeded cleaning procedure. Thus, for example a tube may be subjected in sequence to successive washes of mixed nitric acid and hydrofluoric acid, water and nitrogen, this series being followed by a dilute acid wash, e.g. a 5% solution of hydrofluoric, and finally a water rinse. Because of different wash requirements during a cleaning cycle, and the need to segregate the wash solutions, multiple fluid supplies and multiple flow passages are required. In addition to these requirements, the chemically aggressive nature of the wash solutions dictates fabrication of cleaning equipment from chemically inert materials such as high performance plastics.
Accordingly there is a need for tube washing apparatus meeting the several requirements outlined, and particularly for a cleaning fluid distribution head providing complete coverage of the tube interior, while maintaining separate flow paths for the several fluids used in sequence.